Attention

Attention is a well-researched cognitive function and, historically, is one of the most difficult to define. Four characteristics of attention make it a primary cognitive function for CFD therapy:

• Structurally it is transcranial. By this, we mean to say there is no single structure within the brain that gives rise to attention. Rather attention arises from the integrated, timed, parallel interaction of different structures located in discrete regions throughout the brain. Because of its transcranial nature, developing attention will necessarily stimulate development and efficiency across many brain centers.
• Functionally it is many-facetted. The historical approach to studying attention is to analyze its contextual functions: selective, focused, divided, sustained, and alternating attention. Multiple contextual functions of attention are involved in every aspect of cognition and therefore play a vital role in the manifestation of other cognitive functions.
• Operationally it is comprised of interacting networks. The attentional networks – which themselves are transcranial – include alerting, orienting, and executive control. These network operations play a critical role in selecting relevant information, disregarding the irrelevant, achieving goals, and so forth.
• It gives rise to higher-order functions and even consciousness.

 

Neurology of Attention

Recent research and neuroimaging demonstrate that attention is a transcranial cognitive function, interacting with and having a mutual bi-directional dependency with the sensory system, working memory, long term memory, and higher cognitive functions. Here we consider the neurology of attention from the perspective of its principle operational networks.

Alerting Network

Alerting refers both to the ability to stay vigilant and to being “stimuli sensitive” in anticipation of “high priority” event or stimuli. For example, the driver in a car will (should) remain alert to changing traffic conditions whereas passengers may have little concern for such. Functionally the alerting network is strongly correlated to an individual’s sustained and focused attention (see below).

Two inter-related subnetworks are activated for alerting functions. Exogenous alerting – that is, alerting based on external stimuli received through the senses – is based on the so-called “phasic” operation of the locus coeruleus, which is a small region of the brain stem that is the source of norepinephrine. In its phasic operation, the locus coeruleus releases a large amount of norepinephrine which rapidly (i.e., in a timescale of milliseconds) signals the body to a state of high alert (e.g., the heightened sensitivity when you hear footsteps closing in behind you while walking alone on an unlit street). This subnetwork is also integrated with the anterior cingulate and the orbitofrontal cortices – structures involved in emotion, action, and intentions.

The other subnetwork, endogenous maintenance – the ability to maintain vigilance and focus over time – is associated with activation of the fontal-parietal regions, particularly on the right hemisphere.

Orienting Network

Orienting refers to the selection and prioritization of specific input from the global set of external and internal stimuli / information that may be present at any given time. It is vital for the detection, engagement, and disengagement from attentional targets and is thus strongly related to selective, focused, sustained, and alternating attention functions (see below). This selection of a subset of all information or stimuli present provides improved performance and the capacity for priority processing of the selected information, though at the cost of not being able to process or to store the deselected information.

The orienting system is one of two subsystems that subserve selective sustained attention. The orienting network matures during infancy and is eventually superseded by the executive control system sometime in late adolescence. Thus, sustaining attention to an object or task – an activity which requires effort to inhibit orienting to irrelevant tasks or objects – can be observed to be very difficult for younger school-aged children, but relatively easy for those in high school.

Orienting is linked to the neurotransmitter acetylcholine. It is also linked to the superior parietal lobe, temporal parietal junction, and frontal eye fields. It is believed to be modulated by the basal forebrain.

Executive Control Network

The executive control network handles conflict resolution – that is, prioritizing between salient stimuli – controls divided and alternating attentional functions (see below), and is involved in assessing new situations or performing new tasks.

There is agreement among researchers that this system is also necessary for selective and sustained attention, voluntary inhibition, and the directed exercise of working memory. Executive control is particularly implicated in attention / working memory tasks such as anticipating consequences, monitoring disruptions, modifying behavior, and other goal-directed behaviors.

Traditionally, top-down processes – such as the executive control attentional processes – are believed to be processed by the frontal lobes, particularly the prefrontal cortex and anterior cingulate gyrus. Of interest, some researchers have noted that individuals who experienced concussions in early childhood (i.e., before three years of age) have persistent difficulty with:

• Working memory,
• Impulse control,
• Error awareness,
• Conflict awareness (i.e., the awareness that competing salient stimuli are being prioritized),
• Allocation of attentional resources during updating of working memory, and
• Other areas governed by the executive control network.

Functions of Attention

The ability to effectively select and focus on a limited amount of information from the continuous plethora of available information is critical to learning, setting and achieving goals, and higher-level functions including consciousness. It allows us to take note of salient information, either from external or internal sources, and to block out distractions. It even gives rise to our sense of agency or free will.

There is some disagreement among researchers and authors about the various functional aspects of attention, though. From a therapeutic perspective, such subdivisions are somewhat arbitrary and are only useful for conceptual purposes.It is therefore essential that therapists understand the functions simply as observable behaviors that can be mapped to their respective attention subnetworks.

Therapists should also keep in mind that, at every point in the lifespan, the individual’s attention is a limited-resource, limited capacity, hybrid-autonomous system. We can observe that as the individual matures from infancy into adulthood the various aspects or functions of attention mature and begin to manifest as behavior at different rates. As the individual continues to mature and age, these various functions may decline at differing rates. At all times throughout the lifespan, though, we can anticipate the individual utilizing all his or her attentional resources as efficiently as possible. Attempting to do otherwise is difficult if not impossible – rather like asking your body to be less than efficient with your cardiovascular or immune system in any given moment.

This, of course, does not mean attention is fixed; it is possible to develop the attentional system. It would be ineffectual, though, to attempt to isolate and develop the various attentional functions since the overall attentional system will automatically adjust and switch and balance the functions despite our dedicated, arduous efforts. We instead concentrate on developing the subnetworks (alerting, orienting, and executive control) as indicated by weak functional areas and monitor the changes in attentional behavior or functions.

Selective Attention

Selective attention is the function of concern when the individual is asked to process only one source of available information. Successful maintenance of selective attention requires effort; failure results in distraction. Observed deficits in this type of attention may be the result of a failure to properly process the target information or a failure to inhibit the distracting information. Note, if the individual is experiencing difficulty reading, addressing the selective attention function will be required regardless of the specific reading difficulty, but particularly if the individual is having difficulty with comprehension. In general, if the material is to be learned, the individual must selectively attend to it. Information not selected through the memory encoding process will not be retained, even in the presence of frequent repeating of the information.

According to Load Theory, there are two underlying mechanisms of selective attention: a perceptual selection mechanisms for orienting to relevant items and identifying distractors for excluding distractors; and an active executive control to reject perceived irrelevant distractors and to maintain effort. These mechanisms work with internal (e.g., selecting relevant information from long term memory for processing)and external stimuli and significant loading can occur where the individual is required to select relevant information from both internal and external sources simultaneously.

Selective attention is served by two subnetworks:

• The orienting subnetwork allows for the selection of relevant information and the identification of the irrelevant; and
• The executive control subnetwork sustains the maintenance effort and fine-tunes the selection of relevant information.

The difficulty level of maintaining selective attention depends on:

• The similarity between the target and distractor (high degree of similarity is more difficult);
• The predictability of target location and frequency (spacial and/or temporal predictability decreases difficulty);
• The degree of limbic (emotional) interference (emotional interference increases difficulty);
• The perceptual loading of relevant stimuli (more relevant stimuli leads to less distractibility); and
• The working memory loading (more active processing leads to greater distractibility).

Focused Attention

Focused attention, sometimes called selective sustained attention, depends on the alerting network. It concerns the ability to “respond discretely” to specific stimuli and is crucial for problem-solving and reasoning. Focused attention allows the individual to maintain a state of continuous preparedness for imminent processing of information. This function, along with selective attention, is necessary for the word identification and phoneme decoding skills associated with reading.

Divided Attention

Divided attention describes processing or attending to more than one source of information simultaneously. The same considerations that apply to selective attention also apply to divided attention – with the noted exception that the latter involves more than one source. While individuals frequently engage in divided attention (e.g. having a conversation while driving) with little or no decrement in performance, it is possible to so load the individual with one or more foci of attention that a notable performance decrement will be observable in one or more tasks (e.g. having a heated argument while driving in a heavy traffic will probably not end well).

Attentional resources devoted to divided attention tasks are multidimensional, which explains why some combinations of tasks are easier than others. If simultaneous tasks required different dimensions (such as adding two number while listening for an auditory command), then the amount of shared resources is limited. Conversely, activities that share resources (such as adding two numbers while seeking multiple matches in groups of numbers) will be challenging to perform simultaneously. Resource dimensions include:

• Sensory modality (e.g., visual, auditory, and so forth);
• Processing stage (e.g., encoding, central processing, or responding);
• Information type (e.g., visual/spatial, verbal, and so forth); and
• Response mode (e.g., manual, vocal, and so forth.).

Divided attention requires each of the attentional subnetworks.

Sustained Attention

Sustained attending, also referred to as vigilance, is called upon when the task at hand requires maintenance over a prolonged period – especially when the task requires detection of rarely or unpredictably occurring target events. Sustained attention is an effortful function. It can be negatively impacted by fatigue, stress, long intervals between target events, random spacial appearance of target events, and infrequent cueing of target events. Sustained attention underlies and determines the efficiency of selective and divided attention.

Sustained attention is bi-directional – that is, it can be a “top-down” process driven by internal or goal-activated behavior, or a “bottom-up” process such as may be initiated by sensory inputs. These are overlapping processes that will interact to optimize performance.

In the absence of injury, sustained attention increases from early childhood into adulthood, and tends to show a moderate decline as individuals age. In particular, the frontal-parietal regions of the right hemisphere are believed to be the neural centers for sustained attention.

Alternating Attention

Alternating attention, sometimes called “switching attention,” refers to the rapid shifting of attentional focus. Alternating attention depends on the orienting network. When divided attention is overwhelmed, the individual will automatically switch to alternating attention. When sufficient resources are available, the individual will automatically switch to divided attention. The automatic switching between attentional functions is a matter of maintaining optimal resource usage and processing efficiency within the attentional system.

Alternating attention, along with selective attention, is involved in the preparation of saccadic eye movements – a necessary behavior for efficient reading. The speed with which an individual switches between attentional foci is an indicator of reading comprehension ability and reading accuracy.